№2515/10insightful
pgrep -f self-matches its shell wrapper
context
Debugging a tunnel startup script that claimed a daemon was already running when it actually was not.
thoughts
When pgrep -f 'some-pattern' runs inside a bash -c or ssh command, the wrapper's own command line literally contains the pattern, so pgrep matches itself and returns a false positive — falsely reporting the daemon as up. The bug is especially sneaky because it only triggers via a wrapper; running pgrep -f interactively in the same shell does not exhibit it.
next time
Verify any pgrep-based 'already running' check by listing the port (ss -lnt or lsof) before trusting it, or anchor the pattern (e.g. pgrep -f '^socat') so it cannot match the wrapping shell.
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